Means for reducing starting torque in four-cycle engines



Sept. 24, 1968 J. R. HARKNESS ET AL Re. 26,462

MEANS FOR REDUCING STARTING TORQUE 1N FOUR-CYCLE ENGINES Original FiledMarch 25, 1965 4 Sheets-Sheet 1 mdwfm Joseph RobertEarkness [0 hard 1M5ezlenbznusr aZ'm D Sal-12,1. .2,

Sept. 24, 1968 J HARKNESS ET AL MEANS FOR REDUCING STARTING TORQUE INFOUR-CYCLE ENGINES 4 Sheets-Sheet 2 Original Filed March 25, 1965 JasephEgbert Harlmas Rwharc'? WE'ezZanbmde Juhn I7.

Sept. 24, 1968 J R. HARKNESS ET AL Re. 26,462

MEANS FOR REDUCING STARTING TORQUE IN FOUR-CYCLE ENGINES Original FiledMarch 25, 1965 4 Sheets-Sheet 5 z- .e. z- 7 44 & J

52 I M I4 9 53 H 13 313 5g I U 1 l i Z0 MO so I I2 12 I 17 g l7 g :0 IOdmtymnfo'w Joseph Hubert Hark s Rzahard WSezZenbm l-EShn l7. 551121. &IWW

Sept. 24, 1968 J, HARKNESS ET AL Re. 26,462

MEANS FOR REDUCING STARTING TORQUE IN FOUR-CYCLE ENGINES 4 Sheets-Sheet4:

Original Filed March 25, 1965 EXHAUST BASE CIRCLE 21 Hobart Harkness'imuwfiw Jasap Rzchaz'd WI Selim-27am char )3 John D, 5' 21 Mm UnitedStates Patent Oifice Reissued Sept. 24, 1968 26,462 MEANS FOR REDUCINGSTARTING TORQUE IN FOUR-CYCLE ENGINES Joseph R. Harkness, Germantown,Richard W. Seilcnbinder, Milwaukee, and John D. Santi, West Allis, Wis.,assignors to Briggs & Stratton Corporation, Milwaukee, Wis., acorporation of Delaware Original No. 3,306,276, dated Feb. 28, 1967,Ser. No. 442,621, Mar. 25, 1965. Application for reissue May 12, 1967,Ser. No. 646,744

14 Claims. (Cl. 123182) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

ABSTRACT OF THE DISCLOSURE T o facilitate starting of a four-strokecycle internal combustion engine without detrimentally affecting itsnormal operation: during the compression stroke one of the engine valvesis held ofi its seat (either positively or yieldingly) by apredetermined small distance to relieve compression; and during thepower stroke, that same valve or another one is left substantially freeto move through a predetermined small distance toward and from its seatin response to differences in pressure thereacross for the relief ofsuction if the power stroke is unfired.

This invention relates to internal combustion engines, and moreparticularly to four-stroke cycle engines; and the general purpose ofthe invention is to make the starting of such engines easier by reducingthe torque required to turn the crankshaft of the engine duringstarting.

Patent No. 2,999,491, issued September 12, 1961 to J. R. Harkness,disclosed a method and means for facilitating the starting of afour-stroke cycle engine by providing for the reduction of compressionin the cylinder whenever the engine was being turned over at slow speed,as during starting, and accomplished this with only a very slightsacrifice of compression at times when the engine was operating atnormal running speeds. Briefly, the expedient disclosed in that patentwas a very slight modification of one of the valve cams (preferably thecam that controlled actuation of the intake valve) whereby the cam heldthe valve off of its seat by about .010 in. during movement of thepiston through a substantial portion of its compression stroke, thevalve being thus open while the piston moved from a point aboutoneeighth of its total ascent from bottom dead center to a point atabout five eights of its total ascent, with gradual closure of the valveoccurring after the piston had passed the last mentioned point, untilthe valve was fully closed when the piston reached about three-quartersof its total ascent. With this arrangement the slightly open valveprovided a precisely controlled orifice through which part of the chargebeing compressed escaped from the cylinder, to thus significantly reducecompression during starting, when the piston traveled slowly. At runningspeeds, however, the orifice provided by the partly open valve wasinsignificant and did not detrimentally affect engine performance.

The invention of the above mentioned patent was highly satisfactory, andin fact met with enthusiastic commcrcial acceptance because it greatlyreduced the exertion required for starting small four-cycle engines,such as are commonly used for powering lawn mowers, tillers, small snowblowers, garden tractors and the like, when such engines were equippedwith the conventional and inexpensive rope starter.

However, further research on the starting of small four-cycle engineshas disclosed the possibility of an even greater reduction of startingtorque than was provided by the invention of the aforesaid Harknesspatent. Specifically, it has been discovered that the torque required toturn over an engine equipped with the invention of the Harkness patentis greatest during the power stroke when combustion is not taking place.This is because the piston is then moving downwardly against a pressuredifference due to increasing suction, which suction results from thepartial discharge of gas from the cylinder during the immediatelypreceding compression stroke; and it was found that a substantial forceis required to drive the piston downwardly against that pressuredifference.

With this discovery in mind. it is a general object of the presentinvention to provide means in a four-stroke cycle engine for greatlyfacilitating the starting thereof by relieving compression through asubstantial part of the compression stroke and by relieving suctionduring a subsequent power stroke in which combustion does not takeplace, and wherein said means for relieving suction is automaticallyrendered inoperative by the occurrence in the cylinder of combustion andits resulting pressure.

Another and more specific object of this invention is to provide simplemeans associated with one of the valves of a four-cycle engine forpositively moving the valve [between its open and its closed positions]in its opening and closing directions whenever the valve is more than apredetermined small distance from its closed position, and for renderingthe valve substantially free to move in response to gas pressure forcesacross its head whenever, during a selected portion or portions of theengine cycle, the valve is within said distance of its seated position,so that during such portion or portions of the cycle the valve canautomatically assume either a slightly open position or a fully closedposition depending upon pressure conditions within the cylinder.

More specifically it is an object of this invention to provide, in afour-stroke cycle engine having intake and exhaust valves, and actuatingmeans for each valve comprising a cam and a spring by which theinstantaneous position of the valve is normally established in timedrelation to reciprocation of the piston, means for rendering theactuating means for one of the valves substantially ineffective toestablish the position of the same whenever, during a selected portionor portions of the engine cycle, said valve is within a smallpredetermined distance from its [heat] seat, so that the valve is thenre sponsive to differences between pressure in its manifold and pressurein the cylinder.

From what has just been said it will be apparent that it is an object ofthe present invention, in one of its aspects, to provide means in anengine equipped with the cam of Patent No. 2,999,491 for automaticallyrelieving suction in the cylinder during a power stroke in whichcombustion does not occur, without loss of gas pressure during fullthrottle operation of the engine, to

thus substantially reduce starting torque during both the compressionand power strokes of the engine.

The invention of the aforesaid Harkness patent was primarily useful onsmall single-cylinder engines, since larger engines are usually providedwith power driven starters. Furthermore the very slight loss of fullthrottle power (on the order of 3%) resulting from the expedient of thatinvention was of no practical consequence in a small engine and was inany event a small price to pay for the easier starting that it produced;but on a substantially larger engine such power loss might be criticalduring full throttle operation, or at least might not offset thestarting benefits for which it had been sacrificed. By contrast, it isan object of the present invention in certain of its embodiments to somaterially reduce the starting torque of a four-stroke cycle engine thatan appreciably lighter, more compact and less powerful starting motorcan be used when the invention is applied to a multi-cylinder engine ofsubstantial size, and, moreover, to achieve such reduction in startingtorque without any sacrifice in full throttle power output of the engineor any significant increase in engine weight or complexity, and with theemployment of entirely conventional valve cams.

In connection with the last-mentioned embodiments of the invention it isanother and more specific object of this invention to provide simplemeans in a four-cycle engine, cooperating with one of the valves andcomprising a pair of valve springs of unequal force and means forrestraining one of said springs from imposing biasing force upon thevalve when the valve is spaced a small distance from its closedposition, for subjecting said valve to two ranges of biasing force, inone of which ranges the valve is strongly biased toward its closedposition whenever it is more than a predetermined small distance fromits seat, and in the other of which ranges the valve is lightly biasedaway from its closed position whenever it is within said small distancefrom its seat, to thus enable the valve, during the compression andpower strokes, to automatically assume either its fully closed position,if there is substantial pressure in the cylinder, or a slightly openposition, if there is slight pressure or suction in the cylinder.

A further object of the present invention, achieved in other of itsembodiments, is to retain a coincidental but important advantage flowingfrom the expedient of the above mentioned Harkness patent and residingin the substantial minimization of the effects of kickback which occursin a four-cycle engine in which the ignition system eflects firing ofthe spark plug during the latter part 0 the compression stroke ifcombustion takes place in the cylinder of [an] the engine at a time whenthe crankshaft and flywheel have very little momentum. [Since theignition system of a four-cycle engine normally effects firing of thespark plug during the latter part of the compression stroke, the] Thecrankshaft must be turning at a fairly fast speed in order for it andthe flywheel to have enough inertia to carry the piston through top deadcenter and into the combustion stroke during the early stages ofcombustion. If crankshaft speed is too low, the combusting mixtureforces the piston back down before it reaches the top of its compressionstroke, causing the crankshaft to turn in its reverse direction andproduce the familiar kickback. With the [came] cam arrangement of PatentNo. 2,999,491, the amount of charge taken into the cylinder during anintake stroke was re duced during the subsequent compression stroke asgases were permitted to escape from the cylinder through the slightlyopen intake valve, thus reducing the amount of energy available for akickback; and as the crankshaft backed up in a kickback stroke theintake valve was again lifted slightly off its seat, substantiallyrelieving combustion gas pressure in the cylinder. Because of these twofactors, so much of the force was taken out of kickbacks in an enginehaving the cam arrangement of Patent No.

2,999,491 that an operator might not even notice them. It is thus anobject of the present invention to obtain this same substantialelimination of the effects of kickbacks, concomitantly with theachievement of the other objects of the invention herein set forth.

A further object of this invention is to provide means for reducingstarting torque in a four-stroke cycle engine without incurring anysubstantial sacrifice of engine performance and efficiency, which meansfully comports with essential requirements dictated by practicalexperience, such as: fully automatic operation, extreme simplicity andlow cost, freedom from the need for maintenance, complete reliability,and ready adaptability to existing engine designs without the need forsubstantial modification.

With the above and other objects in view which will appear as thedescription proceeds, this invention resides in the novel construction,combination and arrangement of parts substantially as hereinafterdescribed and more particularly defined by the appended claims, it beingunderstood that such changes in the precise embodiments of thehereindisclosed invention may be made as come within the scope of theclaims.

The accompanying drawings illustrate several complete embodiments of theinvention, constructed according to the best modes so far devised forthe practical application of the principles thereof, and in which FIGURE1 is a fragmentary vertical sectional view of a single cylinderfour-stroke cycle engine incorporating an embodiment of the presentinvention, the engine being shown with the piston moving in itscompression stroke;

FIGURE 2 is a fragmentary view similar to FIGURE 1 but showing theconditions that obtain during starting with the piston moving in itspower or combustion stroke and no combustion occurring;

FIGURE 3 is a view similar to FIGURE 2 but showing the conditions thatexist with the piston moving in its power stroke during normal runningof the engine;

FIGURES 4-7 are views generally similar to FIGURE 2 but showing severalmodified embodiments of the invention;

FIGURE 8 is a composite vertical sectional view showing anotherembodiment of the invention in relation to the intake and exhaust valvesof an engine; and

FIGURE 9 is a view generally similar to FIGURE 2 but showing anothermodified embodiment of the invention intended only for effectingcompression relief durmg starting.

Referring now to the accompanying drawings, and more particularly toFIGURES 1-3, the numeral 5 designates generally the cylinder of afour-stroke cycle engine in which a piston 6 is reciprocable to drive acrankshaft 7 through a connecting rod 8. The engine is provided, as isconventional, with inlet and exhaust poppet valves which control theadmittance of fuel-air mixture to the cylinder from an intake manifoldand the discharge of combustion gases from the cylinder into an exhaustmanifold. In this instance only one of the valves, designated by 9 isshown, and it is illustrated as the inlet valve, although the inventioncould as well be applied to the exhaust valve [as explainedhereinafter].

As is conventional, the valve 9 is actuated by a cam 10 which is rotatedat one-half crankshaft speed by means of timing gears 11 that drivinglyconnect the cam and the crankshaft. As the piston moves downwardly inits intake stroke, the cam 10, acting through a tappet l2 and againstthe bias of a spring 13, holds the valve 9 in a fully open position, sothat combustible mixture can be drawn into the cylinder from a manifold14, all as is conventional. The valve 9 is shown as being conventionalin having an elongated stem 15 at the top of which there is an enlargedcoaxial head 16 that constitues the valve element proper. The spring 13is likewise shown as conventional in that it is a helical compressionspring which substantially coaxially surrounds the stem; and this isalso true of all other springs mentioned hereinafter.

In the embodiment of the invention illustrated in FIG- URES l, 2 and 3,the cam is formed in accordance with the principles disclosed in PatentNo. 2,999,491, and thus has a small lobe or bulge 17 (exaggerated in thedrawings) which holds the valve a predetermined small distance away fromits seat 18 during a substantial portion of the compression stroke.Hence, as explained in said patent, when the piston moves up relativelyslowly, as it does during starting, it can displace out of the cylindera portion of the mixture drawn in during the preceding intake stroke, sothat the piston need not be moved against the force required forcompression of the full charge; but when the piston moves up rapidly inits compression stroke, as it does during normal running operation, onlya negligibly small portion of the mixture charge is displaced out of thecylinder, due to the very small area of the outlet orifice defined bythe partially open valve. Thus, to prevent excessive compression lossduring running operation, the lobe or bulge 17 on the cam 10 holds theinlet valve 9 at a distance from its seat 18 of only about .010 in.

It is a feature of the present invention that as the piston movesdownwardly in its power or combustion stroke, the position of the valve9 depends upon whether or not combustion is taking place in thecylinder, because the valve 9 is responsive to the difference betweenmanifold pressure and pressure in the cylinder whenever the cam isimposing no lift upon the valve and the valve is within a predeterminedsmall distance from its seat; and hence the valve automatically opensslightly to relieve suction in the cylinder during a non-firing powerstroke and automatically closes to prevent loss of pressure gas from thecylinder when combustion takes place during the power stroke. Such fullyautomatic pressure responsive operation of the valve 9 is provided forby reason of the fact that the valve spring 13 is prevented fromimposing its biasing force upon the valve whenever the latter is withinthe above mentioned small distance from its closed position, so that thevalve can move through that distance quite readily in response to gaspressure forces upon its head 16.

The spring 13 has one end bearing against a fixed spring seat 19 thatcan be provided by a part of the engine cylinder body casting, and ithas its other end engaged with an annular force transmitting member 20that loosely surrounds the valve stem 15. The force transmitting memberis substantially cup-shaped, having a circumferential flange 21 whichprojects downwardly, away from the spring 13, and which is engageablewith an upwardly facing abutment surface 22 on the cylinder body thatdefines the limit of motion of the force transmitting member away fromthe spring seat 19. The force which the spring 13 imposes upon the forcetransmitting r member can be transferred to the valve through a washer23 that is anchored to the stem of the valve, beneath the forcetransmitting member, and which provides a unidirectional drivingconnection between the force transmitting member and the valve.

The relationship between the parts just described is such that when thecam 10 forces the valve 9 more than the above mentioned predeterminedsmall distance off of its seat, the spring 13, acting through the forcetransmitting member 20 and the washer 23, strongly biases the valvetoward its closed position, thereby maintaining the valve stem engagedwith the tappet 12, and the tappet with the cam, and insuring promptmovement of the valve away from its fully open position at the propertime near the conclusion of the intake stroke. In other words, theposition of the valve when it is more than said predetermined distancefrom its seat is positively established, in a substantially conventionalmanner, by the valve actuating mechanism comprising the cam 10 and thespring 13.

But as the cam moves toward its power stroke position and permits thevalve to come to said predetermined small distance from its seat, theforce transmitting member bottoms on the abutment surface 22, so thatspring 13 no longer maintains the valve in following relation to the cam10. Hence when the cam is in its power stroke position the valve is freeto move through that small distance, toward and "from its seat, inresponse to gas pressure forces upon its head. In this respect it isnoteworthy that the portion of the cam 10 which rider under the tappet[controls the position of the valve] during the power stroke is entirelyconventional, that is, the cam permits the valve to be engaged with itsseat all during the power stroke and provides for the usual tappetclearance when the valve is closed.

During the exhaust stroke the valve is likewise free to move throughsaid small distance independently of its actuating means comprising thecam 10 and spring 13, but normally of course it remains seated duringthe exhaust stroke because pressure in the cylinder is higher than thatin the intake manifold.

As shown, a small spring 24 at all times reacts between the spring seat19 and the washer 23 to lightly bias the valve 9 toward its closedposition, so that the valve does not open during an unfired combustionstroke until suction in the cylinder exceeds a certain value, and sothat the valve is positively seated during ignited combustion strokes;but it will be apparent that there will be situations in which the lightspring 24 will be unnecessary inasmuch as gravity and inertia forceswill not interfere with response of the valve to pressure forces on itshead.

The size of the small distance through which the valve can float towardand from its seat during the power stroke is determined by variousdesign considerations but is typically on the order of .010 to .020 in.

The modified embodiment of the invention illustrated in FIGURE 4utilizes a cam 10 which is completely conventionali.e., a cam which doesnot have the feature of Patent No. 2,999,491; but the structure shown inFIGURE 4 nevertheless provides for both compression relief and suctionrelief during starting, and has the advantage, moreover, of entailing nosacrifice of gas pressures in the cylinder when the engine is running atfull power output. In this instance the spring 13 which biases the valve9 away from its open position and into following relation with the cam10 reacts between a fixed downwardly facing spring seat 19 on thecylinder body and an annular force transmitting member 120 which isdownwardly dished and which is movable toward and from said spring seat.However, the limit of motion of the force transmitting member away fromthe spring seat 19 is defined by the cam 10', inasmuch as the spring 13at all times maintains the force transmitting member seated on anenlarged head 60 on the upper end of the tappet 12. The lower portion ofthe valve stem extends slidably through the annular force transmittingmember, and an upwardly facing shoulder 28 near the bottom of the stemserves as a stop which defines the limit of upward motion of the valverelative to the force transmitting member. The shoulder 28 can beprovided by a reduced diameter neck portion 26 of the stem that extendsa substantial distance above the shoulder and through the forcetransmitting member. It will be apparent that the spring 13 is effectiveto apply a strong downward biasing force to the force transmittingmemher, but that there is a lost motion connection between the valve andthe force transmitting member.

When the cam is in positions at which it does not impart lift to thevalve and the valve is seated, conventional tappet clearance obtains,that is, there is a gap of a few thousandths of an inch between thebottom of the valve stem and the upper surface of the enlarged head 60on the tappet. However the shoulder 28 is then spaced the abovementioned small distance from the underside of the force transmittingmember 120 so that the valve is free to move to and from its seatthrough that distance independently of its actuating mechanismcomprising the cam, the tappet and the spring 13.

When the cam rotates to a lifting position, as during an intake stroke,the head 60 on the tappet engages the bottom of the valve stem to movethe valve to its open position in a conventional manner. As the camallows the valve to move toward its closed position, the valvesubstantially follows the cam because the lost motion connection betweenthe valve and the force transmitting member permits only a fewthosuandths of an inch of relative motion to take place between thevalve and its actuating mechanism. However, the lost motion connectionbetween the valve and the force transmitting member becomes effectivewhen the cam moves to the position at which it normally allows the valveto seat, since the position of the valve is then determinedsubstantially entirely by its response to the difference betweenpressure in its manifold and pressure in the cylinder, and the actuatingmechanism is ineffective to position it.

A light spring 124, reacting between the head of the valve and a fixedpart of the cylinder body directly therebeneath, urges the valve awayfrom its closed position with a small biasing force. When the engine isbeing started the spring 124 holds the valve the aforesaid smalldistance from its seat against the relatively low gas pressure producedby slow upward movement of the piston through its compression stroke,and of course cooperates with suction in the cylinder to hold the valveopen during an unfired power stroke. But when the engine is running,pressure inside the cylinder during both compression and power strokesexerts enough force upon the head of valve 9 to overcome the bias of thelight spring 124, and hence the valve remains closed during thosestrokes, in accordance with the conventional valve operation.

While the arrangement illustrated in FIGURE 4 is satisfactory inprinciple for either the intake or the exhaust valve, the specificlocation of the spring 124 in the FIG- URE 4 arrangement would subjectthat spring to excessive heat if used on the exhaust valve.

The embodiment of the invention illustrated in FIG- URE 5 is welladapted for either the intake or the exhaust valve. Like the FIGURE 4version of the invention, the FIGURE 5 embodiment [likewise]incorporates an entirely conventional cam not having the feature ofPatent No. 2,999,491, and provides for both compression and suctionrelief during starting without any sacrifice of normal runningperformance or engine efiiciency [if used on the exhaust valve].

In this case. however, the reaction force of a spring 213 which[maintains] tends to maintain the valve 9 in following relationship tothe cam 10' is at all times imposed upon the valve, but said spring issomewhat weaker than a spring 224 which imposes an opposite bias uponthe valve when the valve is within the above mentioned small distancefrom its seat. Hence through that small distanc the valve is lightlybiased away from its seat with a net force equal to the differencebetween the forces exerted by the two springs.

Specifically, spring 213 reacts between a downwardly facing spring seat19 on a fixed part of the cylinder body and a washer-like springretainer anchored to the valve stem 215 near its lower end, so that thebiasing force of the weaker spring is at all times applied to the valve.The stronger spring 224 is received in an upwardly opening well 41 inthe tappet 12 and has its lower end reacting against the bottom of thewell and its upper end engaging a plunger-like force transmitting member320 that is axially slideable in the well. The limit of motion of theforce transmitting member 320 away from the spring seat provided by thebottom of the well 41 is defined by an annular stop 43 which ispress-fitted into the mouth of the well. A reduced diameter sternportion 44 on the force transmitting member extends freely slideablythrough the hole in the annular stop [member] and can project upwardlythereabove to engage the bottom of the valve stem and provide aunidirectional motion transmitting connection between the forcetransmitting member and the valve.

When the cam 10 is in those portions of its orbit in which it permitsthe valve to seat, and there is no substantial pressure in the cylinder,the spring 224, being stronger than spring 213, tends to hold the forcetransmitting member against the annular stop 43, and the stem portion 44of the force transmitting member then projects above the top of thetappet by the above mentioned small predetermined distance plus a fewthousandths of an inch for tappet clearance. As a result, the valvetends to be held at said small distance from its seat under a netbiasing force which is equal to the difference between the forcesexerted by the two springs 213 and 224, such net biasing force beingsufiiciently light so that it can be overcome, and the valve can beseated, by the response of the valve to normal running compression inthe cylinder and of course by the force on the valve due to combustionpro duced pressure. As the cam 10' moves the valve beyond the aforesaidsmall distance from its seat, the valve is maintained in followingrelation to the cam by spring 213, which must be substantially strong.

Under certain circumstances, and [partcularly] particularly with engineshaving aluminum cylinders, the embodiment of the invention shown inFIGURE 6 may have advantages over that illustrated in FIGURE 5, since itpermits more accurate maintenance of the above mentioned smallpredetermined distance in the face of unequal thermal expansion of thevalve stem and cylinder body. It is mainly useful where the invention isapplied to the intake valve, although its principles may have value insome exhaust valve applications. In the FIGURE 6 embodiment, theopposing forces of two springs 313 and 324 of different strengths areagain utilized, but in this instance the net biasing force which theyimpose upon the valve may be employed to bias the valve either toward oraway from its closed position, depending upon results desired, asexplained hereinafter.

One spring 313, which at all times acts upon the valve to urge it towardits closed position, reacts between a downwardly facing spring seat 119fixed on the cylinder body and a washer-like spring retainer 140anchored to the valve stem near the lower end thereof. The other spring324, which is effective upon the valve only when the valve is within theabove mentioned small distance from its closed position, is received inan upwardly opening well 50 in the cylinder body, and the bottom of saidwell provides a seat 51 for the lower end of that spring. The upper endof spring 324 bears against an annular force transmitting member 320which fits loosely in the well and freely slideably surrounds the medialportion of the valve stem so as to be movable toward and from the springseat 51. A stop ring 143 pressed into the mouth of the well provides anabutment against which the force transmitting member 320 is engageableto define the limit of its motion away from the spring seat 51. Areduced diameter lower portion of the valve stem defines a down, wardlyfacing shoulder 52 which cooperates with the force transmitting memberto provide a unidirectional motion transmitting connection between theforce transmitting member and the valve, the actual abutment surface forthe force transmitting member being provided by a C-washer 53 ofaccurately predetermined thickness which is interposed between the forcetransmitting member and the shoulder 52.

It will be apparent that the spring 324 is ineffective to exert biasingforce on the valve when the force transmitting member is engaged withthe annular stop ring 143, and that the C-washer 53 is of such thicknessthat such engagement occurs whenever the valve is at or beyond theaforesaid small distance from its seat. Increasing the thickness of thewasher 53 will increase the length of said small distance. Since theshoulder 52 can be relatively close to the head of the valve, unequalthermal expansion of the valve stem and cylinder body will affect thedistance established by the washer 53 to only a negligible extent.

Since the force of the spring 313 is at all times imposed upon the valvein the direction to seal the same, the two springs act in opposition toone another whenever the valve is within said small distance from itsseat, imposing upon the valve a small net biasing force in one directionof its motion or the other, depending upon which of the two springs 313and 324 is the stronger. As shown, the FIGURE 6 arrangement incorporatesa cam having the small lobe 17 of the above mentioned Harkness patent,whereby the valve is held slightly off its seat during a substantialportion of the compression stroke and whereby, as pointed outhereina'bove, the force of a kickback is substantially relieved. Withsuch a cam, the valve can be subjected, during the power stroke, to avery small net biasing force in the direction to close it, so that it iscapable of opening in response to suction in the cylinder during anunfired power stroke but is positively seated through every power strokein which combustion occurs. To achieve such a net biasing force in thedirection of valve closing, the spring 324 is of course made slightlyweaker than the spring 313. It would also be feasible, with thearrangement illustrated in FIGURE 6, to make the spring 324 somewhatstronger than the spring 313, so that the net biasing force upon thevalve when spring 324 is effective is in the direction to urge the valveaway from its seat; and in that event assurance would be had that evensmall cylinder suctions would be relieved during unfired power strokes,for minimum starting torque, although at the possible sacrifice of asmall degree of fuel economy at lower engine speeds. Obviously it wouldalso be possible to have the springs 324 and 313 of such relativestrengths as to impose a substantially zero net biasing force upon thevalve when spring 324 is effective, so that during every power strok theposition of the valve would at all times be established by thedifference between pressure in the cylinder and pressure in the manifold14.

It will be apparent that an entirely conventional cam, like the cam 10'of FIGURE 5, could be incorporated in the FIGURE 6 embodiment in placeof the cam 10 illustrated therein, but in that event the spring 324would have to be stronger than the spring 313 in order to have the valveslightly off its seat during compression strokes when the engine isbeing turned over during starting.

It will be observed that the FIGURE 6 arrangement, with either type ofcarn, permits conventional tappet clearance to be maintained wheneverthe valve is fully seated. It will also be noted that removal of theC-washer 53 permits the valve seat to be lapped without interferencefrom the spring 324, which cannot be removed after the valve mechanismis assembled into the engine without removal of the press fitted stopring 143.

The embodiment of the invention illustrated in FIG- URE 7 is generallysimilar tothat of FIGURE 4 but with the lighter spring omitted and witha cam 10 having the feature of Patent No. 2,999,491 utilized to hold thevalve 9 spaced at small distance from its closed position during asubstantial portion of every compression stroke. In this case, as in theFIGURE 4 version, the annular force transmitting member 120' is at alltimes maintained in engagement with an enlarged head 60' on the tappetby means of a spring 13 that bears against the force transmittingmember, while a lost motion connection between the valve and the forcetransmitting member renders inoperative the actuating mechanism for thevalve whenever the cam is in a position in which it does not impart liftto the valve, to allow the valve to move through the above mentionedsmall distance to and from its closed position independently of the camand spring. As in the FIGURE 4 version, the valve stem has an axiallyelongated reduced diameter neck portion 26 near its bottom which theforce transmitting member slideably surrounds and which defines anupwardly facing shoulder 28 that provides the lost motion connectionbetween the valve and the force transmitting member. In this case thehead 60' on the tappet is cup-shaped and the annular force transmittingmember 120' [is flat and] has a flat flange that rests on the rim of thehead 60'.

As shown, the valve in the FIGURE 7 embodiment is biased toward its seatby gravity during the power stroke, so that during an unfired powerstroke it is lifted off of its seat solely by suction in the cylinder.If the valve were arranged with its stem normally horizontal, a lightspring could be arranged to react between the shoulder 28 on the valvestem and the underside of the force transmitting member. However itwould not be feasible to bias the valve away from its seat with a lightspring corresponding to the spring 124 in FIGURE 4, because such aspring would tend to hold the valve at the upper limit of its motionrelative to its actuating mechanism, and the lift upon the valveimparted by such a spring would be added to the lift provided by thesmall lobe 17 during the compression stroke, with the result that duringthe compression stroke the valve would be open substantially fartherthan desired. [The] As applied to an imrake valve, the relatively largeorifice thus provided would create a substantial back pressure throughthe intake manifold, interfering with normal functioning of thecarburetor.

The embodiment of the invention illustrated in FIG- URE 8 provides allof the advantages of the invention of the aforesaid Harkness patent,including relief of compression to reduce torque and substantialminimization of the effects of kickback, and at the same time affordsautomatic reduction of suction in the cylinder during an unfired powerstroke in accordance with the present invention, all without entailingany interference with normal functioning of the carburetor. In the FIG-URE 8 embodiment the intake valve 109 is arranged in accordance with theprinciples of the Harkness patent to effect relief of pressure duringthe compression stroke, while relief of suction during an unfiredcombustion stroke is provided for by incorporating the principles of thepresent invention in the exhaust valve 209. The two valves thuscooperate to afford relief of differential pressures across the pistonduring starting.

The spring 13 for the intake valve 109 is at all times effective toproduce a biasing force upon the valve in the direction to close it andmaintain it in following relationship with the cam 10, and the cam hasthe small lobe 17 which holds the valve slightly off its seat during asubstantial portion of every compression stroke, the arrangement of theintake valve actuating mechanism being thus in all respects that of theHarkness patent.

The actuating mechanism for the exhaust valve 209 in the FIGURE 8embodiment has a spring arrangement which is generally similar to thatillustrated in FIGURE 4, although the light spring 424 reacts betweenthe upper surface of the force transmitting member and a downwardlyfacing shoulder 128 on the valve stem, defined by the reduced diameterneck portion 26 near its bottom. However, the light spring 424 must beprevented from lifting the valve 209 off of its seat during the intakestroke (to avoid having exhaust gases sucked back into the cylinderthrough the slightly unseated exhaust valve) and also during thecompression stroke (to avoid an excessively large orifice area forcompression relief). To prevent this, the cam 110 which actuates theexhaust valve 209 has a reduced radius on those portions thereof thatengage the tappet 112 during the intake and compression strokes, whenthe exhaust valve should be kept firmly seated, and has its conventionalradii in those of its peripheral portions that engage the tappet duringthe power and exhaust strokes. Stated another way, the cam 110 is cutdown, through its intake and compression stroke portions, to a radiuswhich is less than that of its base circle by the value of the abovementioned small distance, and has its base circle radius through itspower stroke portion. In this way the valve is seated with tappetclearance when the cutdown portions of the cam 110 are engaged with thetappet; but during the power stroke, when the base circle portion of thecam is engaged with the tappet, the lost motion connection between thevalve and the force transmitting member is effective to permit the valveto move through the above mentioned small distance independently of itsactuating mechanism.

At this point certain general characteristics of the several illustratedembodiments of the present invention can be summarized. The inventionlends itself to incorporation in an engine having the compression reliefarrangement disclosed in Patent No. 2,999,491, and in that case theengine has substantial freedom from kickback. With the special cam ofthat patent spring arrangements like those illustrated in FIGURES 1-3, 6and 7 must be used, since an arrangement like that illustrated in FIG-URE would provide an excessive amount of valve opening during thecompression stroke, interfering with carburetion. With the arrangementsof FIGURES 4 and 7 and such a cam the valve must, during the powerstroke, be under zero bias or (preferably) be lightly biased towards itsseat, to avoid having it open excessively during compression strokes inwhich the engine is turning slowly. With the arrangement illustrated inFIGURES 1-3 the bias upon the valve when it is within the abovementioned small distance from its seat can be either zero or a lightbias towards its seat or a light bias away from its seat.

Using a conventional cam, the principles of this invention can beemployed to effect both compression relief and suction relief duringstarting without affecting the pressure relationships that normallyobtain in the cylinder when the engine is running, and FIGURES 4 and 5depict arrangements by which this result can be Obtained. With aconventional cam, however, the arrangement must incorporate two springs,since the valve must be lightly biased away from its seat whenever it iswithin the above mentioned small distance from its seat, in order toprovide for compression relief during starting. Attention is againdirected to a comparison of FIGURES 4 and 7, which show basicallysimilar arrangements, one using a conventional cam (FIGURE 4) and theother incorporating the cam of Patent No. 2,999,- 491. The FIGURE 5arrangement does not lend itself to incorporation of the cam of thatpatent.

FIGURE 9 discloses another expedient made possible by the presentinvention, whereby only compression relief is provided, but without thespecial cam lobe of Patent No. 2,999,491. The valve 109 of FIGURE 9 isan intake valve, and its spring arrangement is in all respects identicalwith that shown in FIGURE 4. The cam 210 is conventional (i.e., has itsnormal base circle radius and lobe radius) through the intake andcompression stroke portions of its periphery, but [it] is cut down belowits base circle radius by about .010 in. through its power and exhauststroke portions. Hence the valve is lightly biased away from its seat tohold it open about .010 in. during compression strokes when the engineis being started, but seats normally during all power and exhauststrokes and opens normally during intake strokes. As compared with thearrangement disclosed in Patent No. 2,999,491, the FIGURE 9 embodimentof this invention has the advantage that normal cylinder pressures aremaintained during every compression stroke when the engine is running,since pressures in the cylinder are then high enough to seat the valveagainst its bias. Thus the FIGURE 9 version may be useful in cases wherecompression relief is desired for starting without sacrifice of fullthrottle power, and where suction relief is not considered necessary.

From the foregoing description taken with the accompanying drawings itwill be apparent that this invention provides very simple, inexpensiveand dependable means for automatically relieving suction during anonfiring power stroke of a four-stroke cycle engine, without entailingany sacrifice of the full rated power of the engine, and that in certainversions the invention also provides for relief of compression duringstarting by means of simple apparatus comprising a valve, an entirelyconventional cam for the valve, and spring means cooperating with thevalve to render it responsive to varying pressures in the cylinder sothat the valve automatically functions to prevent any loss ofcompression during full power running of the engine.

What is claimed as our invention:

1. A four-stroke cycle internal combustion engine having a pistonreciprocable in a cylinder, intake and exhaust poppet valves forrespectively controlling the admission of combustible mixture into thecylinder from an intake manifold and the discharge of spent gases fromthe cylinder to an exhaust manifold, and actuating means for moving eachvalve between its open and closed positions in timed relation to pistonreciprocation and which actuating means limits the instantaneousdistance of the valve from its seat, said engine being characterized by:

means at all times operatively associated with one of said valves andthe actuating means for the same by which the actuating means isrendered ineffective to affect the position of the valve whenever,during a predetermined portion of the engine cycle in which the pistonis moving through a medial portion of a stroke, the valve is less than apredetermined small distance from its seat, so that during said portionof the engine cycle the valve can respond to differences betweenpressure in its manifold and pressure in the cylinder to assume either aslightly open or a fully closed position, whereby the valve is renderedeffective to significantly reduce any unbalance of pressure on thepiston which retards the same during starting of the engine Withoutsubstantially interfering with normal pressure relationships whichobtain in the cylinder during running of the engine.

2. A four-stroke cycle internal combustion engine having a pistonreciprocable in a cylinder, intake and exhaust poppet valves forcontrolling the flow of gases between the cylinder and intake andexhaust manifolds, respectively, and actuating mechanism for each valvecomprisin g a cyclically moving cam element for moving the valve awayfrom its seat in timed relation to piston reciprocation and a springelement for urging the valve toward its seat and in a direction tomaintain following relationship between the valve and the cam element,said engine being characterized by:

means at all times operatively associated with the actuating mechanismfor one of the valves, operative when the piston is in a medial portionof a stroke [when the cam element for said valve is] in a predeterminedportion of its cycle and the valve is within'a predetermined smalldistance from its seat, by which the spring element for said valve isrendered substantially ineffective to maintain following relationshipbetween the valve and its cam element, so that during said portion ofthe engine cycle the valve can move through said small distance inresponse to the difference between pressure in its manifold and pressurein the cylinder and can therefore assume a slightly open position duringstarting, for significantly reducing anyunbalance of pressure on thepiston that retards" movement of the same, or can close to cause normalpressure relationships to obtain in the cylin' der when the engine isrunning.

3. The internal combustion engine of claim 2, wherein said portion ofthe engine cycle is the power stroke, further characterized by the factthat:

the cam element for said one valve is arranged to positively hold thevalve at a predetermined small distance from its closed position duringa substantial portion of the compression stroke of the engine, to

thus provide a small orifice through which compression can be relievedwhen the engine is being started without incurring substantial loss ofcompression during normal running operation.

4. In an internal combustion engine having a'piston reciprocable in acylinder, intake and exhaust poppet valves for respectively controllingthe admission of combustible mixture into the cylinder from an intakemanifold and the discharge of spent gases from the cylinder to anexhaust manifold, and a plurality of cams, one for each valve, foractuating each valve from its closed to its open position intimed'relation to reciprocation of the piston:

(A) a first spring operatively associated with one of the valves forapplying thereto a strong biasing force toward its closed positionwhenever said valve is more than a predetermined small distance from itsclosed position, so that the position of said valve whenever it is morethan said distance from its closed position is positively established bysaid cam in cooperation with the first spring;

(B) a second spring for applying to said valve a biasing force which isof a different value than the biasing force applied to the valve by thefirst spring; and

(C) means operatively associated with said one valve and the strongerone of said springs for rendering said stronger spring incapable ofapplying biasing force to the valve when the valve is at said distancefrom its closed position, so that whenever the valve is within saiddistance from its closed position, a biasing force is applied to itwhich is light enough to render the valve responsive to dilferencesbetween pressure in its manifold and pressure within the cylinder.

5. A four-stroke cycle internal combustion engine having a pistonreciprocable in a cylinder, intake and exhaust poppet valves forrespectively controlling the admission of combustion mixture to thecylinder from an intake manifold and the discharge of spent gases fromthe cylinder to an exhaust manifold, and means for controlling theposition of each valve in every part of the engine cycle comprisingbiasing means for each valve and unidirectional actuating means for eachvalve movable in timed relation to reciprocation of the piston, saidengine being characterized by the fact that the biasing means for one ofthe valves comprises:

(A) a spring;

(B) means providing a seat against which one end of the spring reacts;

(C) a force transmitting member against which the other end of saidspring reacts and which, has a unidirectional motion transmittingconnection with the valve and is movable in opposite directionsrelatively toward and from the spring seat, and

(D) means for preventing said spring from imposing biasing force uponthe valve when the valve is spaced a predetermined small distance fromits closed position, so that the valve can be moved back and forththrough said small distance by differences between pressure in itsmanifold and pressure within the cylinder, said last named meanscomprising means on the engine engageable by the force transmittingmember to prevent movement of the same beyond a predetermined distancefrom the spring seat. L

6. In a four-stroke cycle internal combustion engine having a pistonreciprocable in a cylinder, intake and exhaust poppet valves forrespectively controlling the admissionof combustion mixture into thecylinder from an intake manifold and the discharge of spent gases fromthe cylinder to an exhaust manifold, and cam means for acmating eachvalve in timed relation to movement of the piston between open andclosed positions and through an intermediate position at which the valveis spaced a predetermined small distance from its seat, means forrelieving suction in the cylinder during a non-firing power stroke, toreduce starting torque, without incurring release of pressure gas fromthe cylinder during a power stroke in which combustion occurs, saidmeans comprising:

(A) a pair of springs, one of which is stronger than the other;

(B) means providing a spring seat against which one end of one of saidsprings reacts;

(C) a force transmitting member against which the other end of said onespring is engaged and which is movable toward and from said spring seat;

(D) means providing a unidirectional motion transmitting connectionbetween the force transmitting member and one of the valves, throughwhich connection said one spring can impose bias in one direction uponsaid one valve;

(E) means on the engine for limiting motion of the force transmittingmember in its direction away from said spring seat, to prevent said onespring from imposing biasing force upon said valve when the valve is atone side of said intermediate position;

(F) means providing a spring seat against which one end of the otherspring reacts; and

(6) means providing a connection between said valve and the other end ofsaid other spring whereby the biasing force of said other spring isimposed upon the valve when it is at said side of its intermediateposition, so that said two springs and their respective connection meanscooperate to provide a strong biasing force for urging the valve towardits closed position whenever the valve is near its open position and abiasing force when it is within said small distance from its closedposition that is light enough to render the valve responsive todifferences between gas pressure in its manifold and gas pressure withinthe cylinder.

7. The internal combustion engine of claim 6 further characterized bythe following:

(A) the first mentioned spring is the stronger and biases the valvetoward its closed position; and

(B) said means for limiting motion of the force transmitting membercomprises a fixed part on the engine against which the forcetransmitting member engages when said valve is at its said intermediateposition so that the valve is relieved of the biasing force of the firstmentioned spring whenever the valve is within said predetermined smalldistance from its seat.

8. The internal combustion engine of claim 7 further characterized bythe fact that:

(A) said last named connection means is so arranged that said otherspring at all times biases the valve toward its closed position with alight force which supplements that of the first mentioned spring whenthe valve is beyond said distance from its seat; and

(B) the cam means for actuating said one valve is arranged to hold thesame out of its closed position by substantially said distance, againstthe bias of said other spring, during a substantial portion of thecompression stroke of the piston.

9. The internal combustion engine of claim 6 wherein the cam means foractuating said one valve comprises a cam and a [tappett] rapper, furthercharacterized by the following:

(A) said means on the engine for limiting motion of the forcetransmitting member away from the first mentioned spring seat comprisesthe tappet, with which the force transmitting member is maintainedengaged by the first designated spring; and

(B) said other spring is weaker than the first memtioned spring andreacts against a part on the valve in the direction to bias the valveaway from its closed position.

10. The internal combustion engine of claim 6, wherein said one valvehas an elongated stem and an enlarged coaxial head, furthercharacterized by the following:

(A) the first spring is the stronger and surrounds the valve stem andreacts against an annular spring seat which is fixed on the engine,surrounding the valve stem, and which faces the valve head;

(B) said force transmitting member comprises an annular member whichslideably surrounds the valve stem;

(C) said unidirectional motion transmitting connection between the forcetransmitting member and the valve comprises a circumferential shoulderon the valve stem which faces away from the head and which is engageableby said annular member;

(D) said means for limiting motion of the force transmitting membercomprises an annular stop lixed on the engine coaxially with the valvestem and facing away from the valve head to be engageable by saidannular member; and

(E) said other spring at all times biases the valve toward its closedposition so that through said small distance the valve is biased awayfrom its closed position with a force equal to the difference betweenthe biasing forces exerted by the two springs.

11. In an internal combustion engine having a piston reciprocable in acylinder, valves for controlling the admission of combustible mixture tothe cylinder and the discharge of spent gases therefrom, and a pluralityof cams, one for each valve, for actuating each valve from its closedposition toward its open position in timed relation to reciprocation ofthe piston:

(A) a first spring operatively associated with one of the valves forapplying thereto a strong biasing force toward its closed positionWhenever said valve is more than a predetermined small distance from itsclosed position, so that the position of said valve whenever it is morethan said distance from its closed position is positively established bysaid cam in cooperation with the first spring;

(B) a second spring for applying to said valve a biasing force which isof a different value than the biasing force applied to the valve by thefirst spring; and

(C) means operatively associated with said one valve and one of saidsprings for rendering said one spring incapable of applying biasingforce to the valve whenever the valve is at said distance from itsclosed position, said last named means comprising (1) a member againstwhich one end of said one spring reacts, said member being movable inand opposite to the direction in which said spring exerts its reactionthereon,

(2) means for limiting motion of said member in the direction in whichsaid spring exerts its reaction thereon, and

(3) means providing a unidirectional driving connection between saidmember and said one valve through which the reaction force of saidspring can be transmitted to said valve.

[12. A four-stroke cycle internal combustion engine having a cylinder inwhich a piston is reciprocable and having intake and exhaust poppetvalves for respectively controlling admission of combustible gases tothe cylinder from an intake manifold and discharge of spent gases fromthe cylinder to an exhaust manifold, said engine being characterized by:

(A) means for moving one of the valves toward and from its seat in timedrelation to piston reciprocation and for positively establishing theinstantaneous position of said one valve whenever it is more than asmall predetermined distance from its seat; and

(B) means for disabling said first mentioned means whenever said onevalve is within said small distance from its seat so that the positionof said one valve when it is within said distance from its seat isdetermined by its response to the difference between pressure in thecylinder and pressure in its manifold] [13. A fourstroke cycle internalcombustion engine having a cylinder in which a piston is reciprocableand having intake and exhaust poppet valves for respectively controllingadmission of combustible gases to the cylinder from an intake manifoldand discharge of spent gases from the cylinder to an exhaust manifold,said engine being characterized by:

means for moving one of the valves toward and from its seat in timedrelation to piston reciprocation and for limiting the instantaneousdistance of said one valve from its seat to different values indifferent predetermined portions of the engines cycle, said meansleaving the valve substantially free to move through a predeterminedsmall distance toward and from its seat during a predetermined portionof the engine cycle in response to the difference between pressure inits manifold and pressure in the cylinder] 14. In a four-stroke cycleinternal combustion engine having a piston reciprocable in a cylinder,intake and exhaust poppet valves, each having an enlarged head and astem extending down from the head, for respectively controlling theadmission of combustible mixture to the cylinder from an intake manifoldand the discharge of spent gases from the cylinder to an exhaustmanifold, a cam for actuating each valve away from its seat in timedrelation to reciprocation of the piston, and a tappet for each valveproviding a motion transmitting connection between the valve and itscam:

(A) means on the engine providing a downwardly facing spring seatadjacent to the stem of one of the valves;

(B) a force transmitting member normally engaged with the tappe: forsaid one valve and providing an upwardly facing spring retainer;

(C) a spring confined under yielding bias between said spring seat andthe force transmitting member to maintain the latter engaged with thetappet; and

(D) cooperating means on the stem of said one valve and on the forcetransmitting member providing a 0st motion connection between themwhereby said valve can move through a predetermined small dislancetoward and from its seat independently of the force transmitting member,so that when the cam for said valve is in a position in which it permitsthe valve f b engage its seat, said valve can move toward and from itsseat in response to differences between pressure in its manifold andpressure in the cylinder and can therefore effect substantial relief ofpressure differences across the piston during starting but can maintainnormal pressure relationships in the cylinder during running of theengine. 15 A four-stroke cycle internal combustion engine having acylinder in which a piston is reciprocable and having intake and exhaustpoppet valves for respectively controlling admission of combustiblegases to the cylinder from an intake manifold and discharge of spentgases from the cylinder to an exhaust manifold, said engine beingcharacterized by:

(A) means for moving one of the valves toward and from. its seat intimed relation to piston reciprocati n and for positively establishingthe instantaneous position of said one valve whenever it is more than asmall predetermined distance from its seat; and

(B) means for rendering said first mentioned means ineffective toestablish the position of said one valve during a substantial portion ofat least one of the compression and power strokes so long as said valveis within said small distance from i s seat so that the position of saidvalve is then determined by its response to the diflerence betweenpressure in the cylinder and pressure in its manifold.

16. A four-stroke cycle internal combustion engine having a cylinder inwhich a piston is reciprocable and haw ing intake and exhaust poppetvalves for respectively controlling admission of combustible gases tothe cylinder from an intake manifold and discharge of spent gases fromthe cylinder to an exhaust manifold, said engine being characterized by:

means for moving one of the valves toward and from its seat in timedrelation to piston reciprocation and for limiting the instantaneousdistance of said one valve from its seat, said means leaving the valvesubstantially free, during a substantial portion of at least one of thecompression and power strokes of the engine cycle, to move through apredetermined small distance toward and from its seat in response to thedifference between pressure in its manifold and pressure in thecylinder.

References Cited patent.

RALPH D.

UNITED STATES PATENTS 12/1920 Spohrer 123-92 12/1962 Colton 12390BLAKESLEE, Primary Examiner.

